An inkjet image forming device, such as an inkjet printer, has conventionally been known, which includes a head that forms and discharges the liquid droplets of a recording liquid, such as ink, through plural microscopic nozzles, based on a method using a movable actuator, such as a piezoelectric method, or a heating film-boiling method, such as a thermal method (cf. Patent Document 1 (Japanese Published Unexamined Application No. H01-130949) and Patent Document 2 (Japanese Registered Patent No. 2724141)), and which performs inkjet recording (cf., Patent Document 3 (Japanese Published Unexamined Application No. 2008-062397), Patent Document 4 (Japanese Published Unexamined Application No. H11-188858), and Patent Document 5 (Japanese Published Unexamined Application No. 2010-188665)).
In the inkjet method, with a configuration in which the recording liquid from the head is directly applied onto a recording material, such as a recording paper, since the head and the recording material are adjacent to each other, paper dust and dust that adhere to the recording material tend to adhere to the nozzles. When the paper dust adheres to the nozzles, flying directions of the droplets discharged from the nozzles may be perturbed and the nozzles may be clogged. Thus the image quality and the reliability are lowered. As a method of circumventing such a problem, usually discharging stability of the nozzles is given priority, and a recording liquid having a low viscosity is utilized. However, when droplets of the recording liquid having the low viscosity adhere onto the recording material, the droplets tend to be blurred.
Accordingly, an image forming device having an intermediate transfer body has been proposed. Namely, the image forming device includes the intermediate transfer body that supports droplets of a recording liquid discharged from a head. In the image forming device, an image is formed on the intermediate transfer body, and subsequently the image is transferred onto a recording material (cf. Patent Documents 3 through 5).
Further, an image forming device having a process liquid applying unit has been proposed. Here, the image forming device also includes the intermediate transfer body. The process liquid applying unit is for applying a process liquid that changes the pH level of the recording liquid onto the intermediate transfer body (cf. Patent Document 3). In the image forming device, the recording liquid is formed of a solvent which consists of a mixture of water and a water soluble solvent, in which at least pigments and polymer particles are dispersed. Here, the pigments and the polymer particles are condensed, when the pH level is changed.
Further, another image forming device having the intermediate transfer body has been proposed. Here, powders that absorb the droplets of the recording paper are adhered on the intermediate transfer body, so as to reduce the blurs (cf. Patent Document 4).
Further, another image forming device having the intermediate transfer body has been proposed. Namely, in the proposed image forming device, in order to address the problem of the blurring, a bridge, which is a liquid column of an electrically-conductive recording liquid, is temporarily formed between a nozzle and the intermediate transfer body and a voltage is applied to the liquid column, so that the water included in the bridge is decomposed by electrolysis (cf. Patent Document 5).
However, the image forming devices, in which the process liquid or the powders are adhered to the intermediate transfer body (cf. Patent Documents 3 and 4), have a problem that the printing speed is reduced due to the adherence of the process liquid or the powders, and a problem that the image forming devices increase in size. Further, with the configuration in which the powders are adhered to the intermediate transfer body, the powders tend to adhere to the nozzles, and the discharging performance of the head to discharge the recording liquid tends to be lowered. Therefore, the problem that the printing speed is reduced and the problem that the image forming devices increase in size may be required to be resolved, while ensuring the discharging performance of the head to discharge the recording liquid.
On the other hand, for the image forming device that temporarily forms the bridge of the liquid column of the electrically-conductive recording liquid between the nozzle and the intermediate transfer body and that applies the voltage to the bridge, so that the water included in the bridge is decomposed by electrolysis (cf. Patent Document 5), there is an advantage that the processing liquid other than the recording liquid and the powder may be not required.
In such an image forming device, in order to suppress the blurring, it is preferable that the recording liquid of the liquid column be sufficiently decomposed by electrolysis. However, when a very high voltage is applied between the nozzle and the intermediate transfer body, so as to facilitate the electrolysis, the required power may increase and the recording liquid may be scattered. Further, when the electric conductivity of the recording liquid is increased, so as to facilitate the electrolysis, the dispersion stability of the pigments may be degraded by the large amount of electrolytes.
An objective of the embodiments is to provide an image forming device that forms images by applying a recording liquid onto an intermediate transfer body through a head. Here, the image forming device can suppress blurring of droplets of the recording liquid without adding a process liquid or powders other than the recording liquid, while ensuring the discharging performance of the head to discharge the recording liquid. Further, the image forming device can suppress the blurring of the droplets of the recording liquid by ensuring that the recording liquid is decomposed by electrolysis without utilizing a high voltage or a large amount of electrolytes. Another objective of the embodiments is to provide an image forming method in which the image forming device is utilized.